1. Field of Invention
The present invention relates to a paper feeder that comprises a mechanism for aligning a front edge of papers that aligns front edges of supplied sheets of paper such as recording papers or documents, and is used for equipment such as a copier and a printer.
2. Description of Related Art
Conventionally, a mechanism for aligning paper front edges that align front edges of papers is installed in a paper feeder for equipment such as a copy machine and a printer in order to prevent plural papers from being fed or to prevent papers from being fed at a tilt or at an angle. This mechanism of aligning paper front edges prevents a problem of plural feeding or tilted feeding of papers when a bundle or stack of papers is pushed too strongly at the paper tray. In the conventional mechanism for aligning paper front edges, the paper front edge alignment member is moved in a vertical direction by a solenoid.
FIG. 13 is a side cross-sectional view that shows the internal structure of the conventional paper feeder. In order to stack papers on a paper supply tray 131, a paper front edge alignment member 133 is moved up by a solenoid 134 and front edge of the paper 132 is abutted against the paper front edge alignment member 133 to align the front edge of the papers 132.
On the other hand, in order to supply the stacked paper 132, the paper edge alignment member 133 is lowered by the solenoid 134 to remove the paper front edge alignment member 133 from the front edge of the paper 132. At the same time the pickup roller 135 moves down on to the surface of the stack of the paper 132 and advances a sheet to the paper feed roller 136 by rotation of the pickup roller 135.
However in such conventional paper feeder, the up and down moving mechanism for the paper front edge alignment member 133 is independent from the movement mechanism for the pickup roller 135. As a result, the structure becomes complicated and needs more space in the equipment. Hence it is an obstacle to the down sizing of the equipment. Further, although the timing of up and down movements of the paper front edge alignment member 133 and the timing of the up and down movements of the pickup roller 135 need to be synchronized. However the timing control is not easy because there two mechanisms are moved up and down by different mechanisms and this has been a cause of paper jams.
In order to solve the above problem, the paper feeder, which mechanically synchronizes the timing of the paper front edge alignment member moving down to the front edge of the papers and the timing of the up and down movement of the pickup roller, has been provided. For example, the timing for a paper front edge alignment member moving down on to the paper and the timing of up and down movement a pickup roller are mechanically synchronized as disclosed in Japanese utility model patent Laid-open No 2-57846.
FIG. 14 shows side cross-sectional views showing the internal structure of this paper feeder. The paper front edge alignment member 143 is mounted for rotation about the rotation shaft 147 of the pickup roller 146. And, the paper front edge alignment member 143 is interlocked with the up and down movement of the pickup roller 146. The paper front edge alignment member 143 has a first protrusion 144 and a second protrusion 145 that extend in different directions. The first protrusion 144 aligns the front edge of stacked paper 142 and the second protrusion 145 engages a separately provided stopper 148.
In this setup, when the paper front edge alignment member 143 moves up by the upward movement of the pickup roller 146, the pivot of the paper front edge alignment member 143 is restricted by the contact of the second protrusion 145 and the stopper 148. As the result, first protrusion 144 stops and aligns the front edge of the paper 142.
On the other hand, when the paper front edge alignment member 143 moves down by the down ward movement of the pickup roller 146, the contact of the second protrusion 145 and the stopper 148 is released, and the pivot control of the paper front edge alignment member 143 is released. As the result, the paper 142 moves by the rotation of the pickup roller 146 and pushes the first protrusion 144. Then the paper front edge alignment member 143 rotates and the first protrusion 144 moves away so that it does not block paper feeding.
In the paper feeder mentioned above, it is possible to achieve downsizing of space requirements because it is not necessary to have separate mechanism for moving the paper front edge alignment member 143. And it is also possible to reliably synchronize the timing of the up and down movement of the paper front edge alignment member 143 and of the pickup roller 146 confidently, because the paper front edge alignment member 143 is provided to pivot about the rotating shaft 147 of the pickup roller 146.
However, in a conventional paper feeder mentioned above, the following problem has occurred. When the pickup roller moves up, the paper front edge alignment member moves up together with it and the second protrusion touches the stopper. As the result, pivoting of the paper front edge alignment member is restricted even when the front edge of papers pushes the first protrusion.
In this situation, if the papers are pushed firmly against the first protrusion, the second protrusion on the other side of the first protrusion is pushed firmly to the stopper because pivoting of the paper front edge alignment member is restricted by the contact of the second protrusion and the stopper.
In this case, the stronger the pushing force of the second protrusion against the stopper, larger the friction between the second protrusion and the stopper becomes. If the pickup roller is moved down in this situation, the pickup roller does not move down smoothly because of the friction, and as a result it is possible that paper feed is prevented.
An object of the present invention is to provide a paper feeder that can reliably synchronize the up and down movements of the paper front edge alignment member and of the pickup roller. Another object of the present invention is to provide a paper feeder that can smoothly move the pickup roller even in the event that papers are firmly pushed against the paper front edge alignment member.
In the present invention, in order to solve the problem mentioned above, the paper feeder comprises a pickup roller that is provided to be movably in a vertical direction, and moves down towards the upper surface of stacked papers to advance a paper to a paper feed roller, a front edge alignment member that is pivotably mounted, and aligns the front edge of the stacked papers, a stopper that is pivotably mounted, and restricts the pivoting the front edge alignment member, and a stopper releasing section that releases the stopper from the front edge alignment section by rotating the stopper, in synchronization with the downward movement of the pickup roller.